WO2012056584A1

WO2012056584A1 - Ad-hoc network communication device, communication system and communication method

Info

Publication number: WO2012056584A1
Application number: PCT/JP2010/069374
Authority: WO
Inventors: 弘起佐藤
Original assignee: 株式会社日立製作所
Priority date: 2010-10-29
Filing date: 2010-10-29
Publication date: 2012-05-03
Also published as: JP5514323B2; JPWO2012056584A1

Abstract

The purpose of the present invention is to provide a wireless ad-hoc network for transmitting data from a large number of communication devices to a data collection communication device with a relatively high degree of reliability. The ad-hoc network has a tree structure and comprises a plurality of communication devices which are connected to each other by means of wireless communication. A communication device (100) is provided with: time-slot management units (119, 120) for managing time slots; and a transmission timing management control unit (117) which acquires a time slot from another communication device (101) or allocates a time slot to another communication device (101), by way of a communication unit (113).

Description

Ad hoc network communication device, communication system, and communication method

The present invention relates to an ad hoc network communication device, a communication system, and a communication method.

Ad hoc network is one of the network construction methods mainly using various wireless communications. An ad hoc network is a network configured by autonomously connecting communication devices without requiring a dedicated base station or router. Ad hoc networks often do not require routing settings and the like in routers, wireless communication devices, etc., as compared to infrastructure networks.

In an ad hoc network, when communication devices exist in a place where wireless communication does not reach each other, the communication devices cannot directly transmit / receive data. Therefore, in an ad hoc network, generally, a communication device that exists within a wireless reachable range serves as a relay, and performs multi-hop communication that transfers data like a so-called bucket relay.

The specification study and standardization activities related to ad hoc networks are being carried out mainly by the Internet Engineering Task Force (IETF) MANET (Mobile Ad-hoc Networks) working group and ROLL (Routing Over Low power and Lossy networks).

Non-Patent Document 1 describes standard specifications of MANET. Non-Patent Document 2 describes the specification of a reactive routing protocol that constructs a routing table for the first time when a communication device starts communication in an ad hoc network. Non-Patent Document 3 describes the specifications of a proactive routing protocol in which communication devices periodically exchange information and construct a routing table in advance in an ad hoc network. Non-Patent Document 4 describes a routing protocol specification in an unstable and low-power wireless network. Non-Patent Document 4 is mainly used when constructing an optimal routing table in a sensor network in which a low-performance communication device including a sensor collects sensing data.

A sensor network is generally constructed by an ad hoc network, and a large number of devices (several hundreds or more) equipped with sensors collectively collect sensing data measured by each device (hereinafter referred to as “data collection device”). )). The sensor network is mainly used in a system that collects data from a large number of communication devices belonging to a predetermined network within a predetermined time. Specifically, it is used for a remote monitoring system such as a factory or a building, a smart grid system, a system for monitoring various states of a house, and the like.

However, if a large number of communication devices transmit data to the data collection device all at once, there is a possibility of causing a collision of communication data. Therefore, for example, Patent Document 1 describes a technique in which each communication device transmits data only during a transmission possible period assigned by a base station. Thereby, collision of communication data is avoided.

JP 2010-21894 A

One method of avoiding communication data collision in wireless communication is a time division method. The time division method is a method for avoiding a collision of communication data by transmitting data only in a communication device to which the time slot is assigned in a predetermined time interval (hereinafter, “time slot”).

The following method can be considered as a method for determining which time slot is assigned to which communication device. First, each communication device transmits information necessary for calculation of time slot allocation to a device (hereinafter referred to as “calculation device”) that performs the calculation. Next, the calculation device calculates an optimal time slot allocation based on the received information. Next, the calculation result (that is, the time slot allocation result) is returned to each communication device.

However, in a sensor network, it is difficult to assign time slots in this way. This is because in a sensor network, since the number of communication devices is very large, a collision of communication data occurs when a large number of communication devices transmit their information (data) all at once to a computing device. That is, there is a high possibility that the computing device cannot receive data necessary for calculating the time slot assignment from each communication device. Furthermore, even if the computing device can receive the data, when transmitting the calculation result to a large number of communication devices, there is a possibility that the calculation result cannot be transmitted because a communication data collision occurs again.

Therefore, an object of the present invention is to reduce the collision of communication data in an ad hoc network in which a large number of communication devices exist, such as a sensor network, so that the communication devices can perform stable communication.

The ad hoc network communication device of the present invention is a communication device belonging to an ad hoc network in which a plurality of communication devices are connected to each other by wireless communication, and transmits a data to and from another communication device. A time slot management unit for managing a time slot indicating information on timing to be acquired, and a time slot is acquired from another communication device or distributed to another communication device through the communication unit, and the acquired or distributed time slot is managed in time slot And a transmission timing management control unit that transmits data to another communication device through the communication unit based on the timing described in the time slot managed by the time slot management unit.

In a preferred embodiment, the transmission timing management control unit may determine the number of time slots to be acquired from other communication devices or distributed to other communication devices based on a predetermined condition.

At this time, as a predetermined condition, the number of time slots may be determined based on a logical network distance between a communication device that acquires or distributes time slots and a predetermined communication device that collects data. .

Furthermore, as a predetermined condition, the number of time slots may be determined based on the width of a communication band with another communication device that acquires or distributes time slots.

Furthermore, when time slots are distributed to other communication devices, when the communication band is narrow, more time slots may be distributed than when the communication band is wide.

Further, the communication device holds a rank value indicating the priority of the communication device, and as a predetermined condition, the rank value held by the communication device and another communication device that acquires or distributes the time slot holds. The number of time slots may be determined based on the difference from the rank value.

In a preferred embodiment, the transmission timing management control unit may distribute or acquire a plurality of time slots that are successively executed from other communication devices.
Thereby, the data held by the communication device can be delivered to the data collection device earlier.

In a preferred embodiment, the transmission timing management control unit checks whether or not it is connected to another communication device, and if there is no response from the other communication device for a predetermined time, the other communication device You may collect the time slots allocated to

This makes it possible to use finite time slots effectively.

In a preferred embodiment, when the transmission timing management control unit is requested by another communication device to acquire a time slot, if the communication device has insufficient time slots to be distributed, the communication device May request the third communication device to acquire a time slot.
Thereby, a finite time slot can be allocated effectively.

1 is a configuration example of an ad hoc network communication system according to an embodiment of the present invention. An example of an ad hoc network communication route table. An example of a transmission timing management table. An example of a self-information management table. An example of the flowchart which shows the process outline | summary of the whole communication apparatus. An example of the flowchart of a time slot request | requirement process and a time slot allocation process. An example of the flowchart of a time slot update process. An example of a flowchart of a time slot return request process. An example of the flowchart of a time slot arbitration process. 1 is an example of a network topology of an ad hoc network according to a first embodiment. 10 is an example of a time slot distribution method considering a change in network topology according to the second embodiment. 10 is an example of a time slot distribution method in consideration of communication characteristics according to the third embodiment. Explanatory drawing of the time slot when the number of the time slot which concerns on Example 5 is not set as a serial number.

Hereinafter, an ad hoc network communication system according to an embodiment of the present invention will be described with reference to the drawings.

Before describing the system configuration of the first embodiment, an outline of the present embodiment will be described.
FIG. 10 is an example of a network topology of the ad hoc network according to the first embodiment. Here, an outline of the operation of the ad hoc network according to the present embodiment will be briefly described. The network topology is a logical communication path for data, and is different from a communication path physically connected by wireless or wired communication.

The sensor network can be configured with a tree-type network topology as shown in FIG. For example, in FIG. 10A, it is assumed that the communication apparatus 1001 (A) is a data collection apparatus or a gateway (hereinafter “GW”) apparatus for another network. Data collected by the communication device 1003 (D) using a sensor or the like is transmitted to the communication device 1001 (A) via the communication device 1002 (B). Hereinafter, the communication device 1001 (A) is the communication device (A), the communication device 1002 (B) is the communication device (B), the communication device 1003 (D) is the communication device (D), and the communication device 1004 (E). May be abbreviated as a communication device (E).

∙ Each time slot is assigned a number and is executed in the order of the assigned number. Each communication device (A) to (G) is assigned a time slot as shown in FIG. 10 (a).

In the illustrated example, the communication device (A) distributes all time slots to the subordinate communication devices, so there is no time slot. The communication device (B) located immediately below the communication device (A) has one time slot (1). Similarly, the other communication device (C) located immediately below the communication device (A) also has one time slot (6).

The communication device (D) located immediately below the communication device (B) has two continuous time slots (2) and (3). The other communication device (E) located immediately below the communication device (B) has two other continuous time slots (4) and (5).

Similarly, the communication device (F) located immediately below the communication device (C) has two consecutive time slots (7) and (8). The other communication device (G) located immediately below the communication device (C) has two other continuous time slots (9) and (10).

The time slot number indicates the transmission timing from the reference time. Each of the communication devices (A) to (G) shares a reference time. When the time corresponding to the held time slot number arrives, each communication device (A) to (G) transmits the data (measurement data) held so far to the higher-level communication device. The final destination of the data is the communication device (A).

The host communication device viewed from the communication devices (D) and (E) is the communication device (B). Similarly, the host communication device viewed from the communication devices (F) and (G) is the communication device (C). The host communication device viewed from the communication devices (B) and (C) is the communication device (A). *

When the time corresponding to the time slot (1) arrives, the communication device (B) can transmit data to the communication device (A). At the time corresponding to the time slots (2) and (3), the communication device (D) can transmit data to the communication device (A) using the higher-level communication device (B) as a relay device. Since the communication device (D) has two consecutive time slots (2) and (3), the communication device (D) can hop twice in succession and promptly deliver data to the communication device (A). Can do.

When the time corresponding to the time slots (4) and (5) arrives, the communication device (E) communicates with the communication device (A) via the communication device (B) as described in the communication device (D). Data can be transmitted. When the time corresponding to the time slot (6) arrives, the communication device (C) can transmit data to the communication device (A) as described in the communication device (B).

Similarly, when the time corresponding to the time slots (7) and (8) arrives, the communication device (F) uses the higher-level communication device (C) as a relay device and sends data to the highest-level communication device (A). Can be sent. When the time corresponding to the time slots (9) and (10) arrives, the communication device (G) can transmit data to the communication device (A) via the communication device (C).

Further, for example, data collected by the communication device (D) is transmitted to the communication device (B) at the timing of the time slot (2) 1012 shown in FIG. The communication device (B) transfers the data received from the communication device (D) to the communication device (A) at the timing of the time slot (3) 1013.

Thereby, the data collected by the communication device (D) by the sensor or the like can be transmitted to the communication device (A).

When distributing time slots to communication devices located downstream in a logical network, check the logical network distance (for example, the number of hops) between the local device and the data collection device. It is desirable to distribute the number of time slots by serial numbers. Since the time slots are executed in numerical order, the data can reach the data collection device (A) earlier. In this specification, in the logical network, the data collection device (A) side is referred to as upstream, and the end sides (D) to (G) of the tree are referred to as downstream.

Here, for example, the communication speed between the communication devices of the sensor network is about 4.2 kbps, which is considerably slower than a wireless LAN (Local Area network) or the like. Therefore, in the sensor network, the time interval of one time slot is set to about 500 msec. In addition, said numerical value is an illustration for description, Comprising: The range of this invention is not limited.

FIG. 1 is a configuration example of an ad hoc network communication system according to an embodiment of the present invention. In this communication system, one communication device 100 and the other communication device 101 constitute a wireless ad hoc network. Hereinafter, the communication device 100 will be mainly described. The communication device 100 is connected to one server 140 via one network network 130, and is also connected to the other server 141 via the other network network 131.

When viewed from the ad hoc network side, the

network networks

130 and 131 are different networks from the ad hoc network. The

network networks

130 and 131 are, for example, a mobile phone communication network, an optical line network, or a public wireless LAN network.

The communication device 100 includes a CPU (Central Processing Unit) 111, a memory 112, and a storage unit 114. Various programs included in the communication device 100 are stored in the storage unit 114, and are read and executed by the CPU 111 via the memory 112 as necessary. The communication device 100 is connected to network

networks

130 and 131 via a communication unit 113.

The communication unit 113 includes a first communication interface for performing ad hoc network communication with the other communication device 101 and a second communication interface for connecting to the

network networks

130 and 131. The communication unit 113 performs various communication controls such as selection of the

network networks

130 and 131, disconnection from the

network networks

130 and 131, packet transmission / reception, determination of communication availability, and measurement of communication volume via the first communication interface. . Further, the communication unit 113 may use, for example, a wireless LAN ad hoc mode, specific low power wireless communication, or a dedicated network device as a second communication interface for performing ad hoc network communication.

In the storage unit 114, a communication control unit 115, an ad hoc network communication control unit 116, and a transmission timing management control unit 117 are stored as programs. In addition, an ad hoc network communication path table 118, a transmission timing management table 119, and a self information management table 120 used for various controls are stored as data.

The transmission timing management table 119 is a table for managing transmission timing. The transmission timing management table 119 manages time slots. The time slot indicates information related to the timing at which the communication apparatus 100 transmits data collected by a sensor or the like to another communication apparatus 101. The transmission timing management table 119 corresponds to a “time slot management unit” together with a self-information management table 120 described later.

The communication control unit 115 controls communication with the

servers

140 and 141 via the

network networks

130 and 131. A communication protocol used for communication control is, for example, TCP / IP. However, other communication protocols may be used.

The ad hoc network communication control unit 116 is in charge of communication control when building an ad hoc network. The ad hoc network communication control unit 116 uses other routing protocols such as AODV (Ad hoc On-Demand Distance Vector) or OSLR (Optimized Link State Routing Protocol) to detect other communication devices 101 and Perform construction.

The transmission timing management control unit 117 acquires a time slot from another communication device 101 or distributes it to the other communication device 101 through the communication unit 113. The acquired or distributed time slot is stored in the transmission timing management table 119. The transmission timing management control unit 117 transmits data to another communication apparatus 101 based on the transmission timing described in the time slot.

For example, the transmission timing management control unit 117 performs management of the time slot of the own device 100, management of data transmission timing of the own device 100, and arbitration of time slots with other communication devices 101. Here, arbitration of time slots with other communication devices 101 means that some or all of the time slots held by the own device 100 are distributed to other communication devices 101, or the number of time slots of the own device 100. In order to increase the time slot, a time slot is obtained from another communication apparatus 101.

The transmission timing management control unit 117 may determine the number of time slots acquired from the other communication apparatus 101 or the number of time slots to be distributed to the other communication apparatus 101 based on a predetermined condition.

For example, the transmission timing management control unit 117 may determine the number of time slots based on the logical network distance between the communication device 100 that acquires or distributes the time slots and the data collection device. .

The transmission timing management control unit 117 may determine the number of time slots based on the width of a communication band with another communication apparatus 101 that acquires or distributes time slots. When distributing time slots to other communication apparatuses 101, when the communication band is narrow, more time slots may be distributed than when the communication band is wide.

Each communication apparatus retains a rank value indicating priority, and the transmission timing management control unit 117 determines the rank value retained by the own apparatus 100 and the rank retained by another communication apparatus 101 that acquires or distributes time slots. The number of time slots may be determined based on the difference from the value.

The transmission timing management control unit 117 may distribute a plurality of time slots that are continuously executed to other communication devices 101 or obtain from other communication devices 101.

The transmission timing management control unit 117 checks whether or not it is connected to another communication apparatus 101, and if there is no response for a predetermined time from the other communication apparatus 101, it is distributed to the other communication apparatus 101. You may make it collect | recover a time slot.

When the transmission timing management control unit 117 is requested by another communication device 101 to acquire a time slot, if the own device 100 has insufficient time slots to be distributed, the own device 100 The communication device may be requested to acquire a time slot, and the acquired time slot may be distributed to other communication devices 101.

Note that details of the processing related to the transmission timing management control unit 117 will be described later.

In this embodiment, the communication control unit 115, the ad hoc network communication control unit 116, and the transmission timing management control unit 117 are stored as programs in the storage unit 114 and executed by the CPU 111. Instead, at least a part of these functions may be realized by a dedicated hardware device.

The server 140 includes a CPU 151, a memory 152, and a storage unit 154. Various programs included in the server 140 are stored in the storage unit 154 and read and executed by the CPU 151 via the memory 152 as necessary. The server 140 further includes a communication unit 153 and is connected to the network 130.

The communication unit 153 performs various communication controls such as selection of the

network networks

130 and 131, disconnection from the

network networks

130 and 131, packet transmission / reception, communication availability determination, and traffic volume measurement.

In the storage unit 154, a communication control unit 155 is stored as a program. In addition, a communication path table 156 and a connection device management table 158 used for various controls are stored as data.

The communication control unit 155 generates a communication path table 156. Further, the communication control unit 155 performs communication control when communicating with other devices via the network 130.

Note that the program may be stored in the storage unit 154 in advance, or may be acquired via a storage medium or a communication network and stored in the storage unit 154 as necessary.

FIG. 2 is an example of the ad hoc network communication path table 118. The ad hoc network communication path table 118 manages the configuration and state of the ad hoc network communication path. The ad hoc network communication path table 118 holds a communication device name 201, a link state 202, a rank 203, and a communication quality 204.

The communication device name 201 is information for identifying a communication device belonging to the ad hoc network. The link status 202 is information indicating whether or not communication is possible and the status. The rank 203 is information indicating how far each communication device is from the data collection device in the network. The communication quality 204 is a value obtained by indexing the communication quality of the ad hoc network communication path. The ad hoc network communication path table 118 is used when a network topology is constructed using a routing protocol such as AODV or OSLR. The ad hoc network communication path table 118 can be created by exchanging information such as the communication state and the number of hops between communication devices constituting the ad hoc network.

FIG. 3 is an example of the transmission timing management table 119. The transmission timing management table 119 holds information related to the time slot of each communication device recognized by the own device 100. For example, the transmission timing management table 119 includes a communication device name 301, a communication device status 302 indicating acquisition or distribution of a time slot, an effective time 303 indicating an acquisition or distribution effective time, and a time of the own device 100. The number of slots 305 is held.

Each time slot is assigned a different number. For example, the communication device to which the tenth time slot is assigned transmits data in the time slot of the tenth time slot from the reference time. It is assumed that the time of each communication device belonging to the ad hoc network is synchronized.

FIG. 4 is an example of the self-information management table 120. The self information management table 120 holds various types of information about its own communication device (own device). For example, the self-information management table 120 holds a status 401, a rank 402, a distribution priority policy 403, and a time slot number 404.

The status 401 is information indicating the current state of the communication device. The status 401 indicates, for example, “normal mode” during normal operation, “arbitration mode” in which time slots are arbitrated with other communication devices, and “stop mode” in which no time slots are used. The rank 402 is information indicating the distance on the network between the device itself and the data collection device. The distribution priority policy 403 is information indicating a determination criterion for distributing time slots. The number of time slots 404 is information indicating the number of time slots currently owned by the own device.

The allocation priority policy 403 defines a policy that assigns time slots to other communication devices when there is a request for time slots from other communication devices. The allocation priority policy 403 may include, for example, a small amount of time slots for one's own time slot, or many times at a time so that other communication devices can actively distribute to other communication devices. It is possible to set whether or not to distribute slots.

The number of time lots to be distributed may be determined according to the rank of the communication device to be distributed. For example, a communication device with a higher rank distributes many time slots because there is a possibility that a large number of communication devices may be connected under the rank. On the other hand, it is possible to limit the time slots to be distributed to lower rank communication devices.

FIG. 5 is an example of a flowchart showing an outline of overall processing of the communication apparatus.
First, the communication apparatus 100 constructs a communication path (501).

Next, the communication apparatus 100 determines whether a time slot request is required (502). If it is determined that a time slot request is necessary (502: Yes), slot request processing is executed (503), and the process proceeds to step 504. On the other hand, if it is determined that a time slot request is unnecessary (502: No), the process proceeds to step 504.

Time slot request processing is necessary when, for example, the value of the number of acquired time slots 404 in the self-information management table 120 is 0, when joining the ad hoc network for the first time, or when the sensing data has increased rapidly This is the case when the required communication bandwidth is required. Details of the time slot request process will be described later.

Next, the communication apparatus 100 determines whether or not the time slot needs to be updated (504). When it is determined that the time slot needs to be updated (504: Yes), time slot update processing is executed (505), and the process proceeds to step 506. On the other hand, if it is determined that updating of the time slot is unnecessary (504: No), the process proceeds to step 506.

The case where the time slot update process is necessary is, for example, the path with the communication apparatus (the source of the time slot) to which the own apparatus is allocated the time slot in the link state 202 of the ad hoc network communication path table 118. Or when the valid time 303 of the time slot of the own device in the transmission timing management table 119 expires, or when it is necessary to reconfirm the time slot assignment by changing the communication path. Details of the time slot update process will be described later.

Next, the communication apparatus 100 determines whether it is necessary to distribute time slots (506). If it is determined that time slot distribution is necessary (506: Yes), slot distribution processing is executed (507), and the process proceeds to step 508. On the other hand, if it is determined that time slot distribution is unnecessary (506: No), the process proceeds to step 508. The case where the time slot distribution process is necessary is, for example, a case where the own apparatus receives a time slot distribution request. Details of the time slot distribution process will be described later.

Next, the communication device 100 determines whether it is necessary to return the slot (508). If it is determined that slot return is necessary (508: Yes), slot return processing is executed (509), and the process proceeds to step 510. On the other hand, if it is determined that the slot return is unnecessary (508: No), the process proceeds to step 510. When the time slot return process is necessary, for example, when a time slot return request is received from another communication device, the time slot allocated when the own device leaves the ad hoc network is assigned to the communication device. Or when returning a time slot which has been acquired once but judged unnecessary to the communication device as a distribution source. Details of the time slot return process will be described later.

Next, the communication device 100 determines whether or not arbitration of the time slot is necessary (510). When it is determined that time slot arbitration is necessary (510: Yes), time slot arbitration processing is executed (511), and the process proceeds to step 512. On the other hand, when it is determined that time slot arbitration is unnecessary (510: No), the process proceeds to step 512. When the time slot arbitration process is necessary, for example, a time slot distribution request has been received from another communication device, but there is no time slot that can be distributed, and in order to distribute time slots from other communication devices For example, it is necessary to acquire Details of the time slot arbitration process will be described later.

Finally, the communication device 100 updates the time slot management table (512). Updating the time slot management table is updating the transmission timing management table 119 and the self information management table 120. If necessary, the ad hoc network communication path table 118 may be updated in step 512. For example, the ad hoc network communication path table 118 may be updated when deleting a communication path with a communication apparatus that has failed to adjust the time slot.

In the flowchart of FIG. 5, each process is executed in order, but the order is not limited. Each table may be updated as appropriate.

FIG. 6 is an example of a flowchart showing time slot request processing and time slot distribution processing. In the process of FIG. 6, the communication device A as the “first communication device” requests a time slot from the communication device B as the “second communication device”, and the communication device B allocates the time slot to the communication device A. Give.

First, the communication device A transmits a time slot request message describing the number of time slots required by the own device to the communication device B (601). The communication device B receives the time slot request message from the communication device A (602).

The communication device B that has received the time slot request refers to the self-information management table 119, confirms the status of the time slot held by the self-device, and determines whether time slot arbitration is necessary (603). When it is determined that arbitration is necessary (603: Yes), a standby message is transmitted to the communication device A (604), and time slot arbitration processing is executed (605). On the other hand, if it is determined that arbitration is not required (603: No), the process proceeds to step 610.

Whether the time slot arbitration is necessary or not may be determined immediately from the time slot availability of the own device, or a time slot request message from another communication device is received for a predetermined time, The determination may be made according to the number of time slot requests received within the time.

Note that a case where unicast communication is performed will be described as an example between the communication device A and the communication device B. However, instead of this, broadcast communication or multicast communication is used to all the surrounding communication devices all at once. A time slot request message may be transmitted. In addition, information indicating the urgency of the time slot may be described in the time slot request message.

Next, the communication device A determines whether a standby message has been received (606). When a standby message is received (606: Yes), a timeout time to be set is set (607). After the timeout is completed (608: Yes), the time slot request message is retransmitted to the communication apparatus B (609), and the process proceeds to step 606. On the other hand, when the standby message has not been received (606: No), the process proceeds to step 613.

The timeout time that is the standby time may be set in advance as a predetermined time, or the communication device B may determine the timeout time and transmit it to the communication device A. Furthermore, when the communication device B determines the timeout time, a predetermined time when a time slot request message from another communication device is received or a time required for time slot arbitration processing (for example, how many hops ahead) It may be determined in consideration of whether it is assumed. Further, in the retransmission of the request message of the communication apparatus A, the number of retransmissions may be set in advance, and the request message may not be retransmitted after the number of retransmissions.

Next, the communication apparatus B determines whether there is a time slot that can be distributed (610). When there is a time slot that can be distributed (610: Yes), a time slot supply message describing the number of time slots to be distributed, the number of time slots, the transmission timing, and the like is transmitted to the communication device A (611). On the other hand, when there is no time slot that can be distributed (610: No), a time slot supply impossible message is transmitted to the communication device A (612).

Finally, the communication device A confirms the reply message from the communication device B (613), and confirms whether the time slot has been acquired (614). If the time slot can be acquired (614: Yes), the time slot management table of the own apparatus is updated (615), and the process is terminated. On the other hand, when the time slot cannot be acquired (614: No), the process is terminated.

In this embodiment, the communication device A receives a reply message only from the communication device B. Alternatively, the communication device A may receive a reply message from a plurality of communication devices, and acquire a time slot from an optimum communication device among the communication devices that have transmitted the reply message. At that time, a time slot that is no longer used may be returned to the communication device that is the distribution source.

FIG. 7 is an example of a flowchart of time slot update processing. In this process, the communication device A updates and confirms the time slot.

First, the communication device A refers to the ad hoc network communication route table 118 and determines whether or not the communication route of the communication device B exists (701). If there is a communication path with the communication device B (701: Yes), the process proceeds to step 702. On the other hand, if there is no communication path with the communication device B (701: No), the process proceeds to step 703.

The communication device A refers to the transmission timing management table 119 and determines whether or not the valid time 303 of the communication device B has been exceeded (702). When the time slot is exceeded (702: Yes), a time slot confirmation message is transmitted to the communication apparatus B in order to confirm whether or not the time slot allocated from the communication apparatus B can be used (703). On the other hand, when it does not exceed in step 702 (702: No), the process is terminated.

The communication device B receives the time slot confirmation message from the communication device A, and transmits a time slot confirmation response message in response to the message to the communication device A (704). The time slot confirmation message and the time slot confirmation response message may be transmitted a plurality of times when the communication quality is poor.

The communication device A receives the time slot confirmation response message transmitted from the communication device B, and determines whether the time slot allocated from the communication device B can be used continuously (705). If it can be used continuously (705: Yes), the valid time 303 of the communication device B is updated in the transmission timing management table 119 (706). On the other hand, if it cannot be used continuously (705: No), the valid time 303 of the communication apparatus B is set to 0 or deleted in the transmission timing table 119 (707).

The method of determining whether or not the communication device A can continue to use the time slot is, for example, whether or not the time slot confirmation response message has been received within a predetermined time, or whether the time slot confirmation response message indicates the time slot. Judgment is made based on whether or not permission to continue use is indicated.

FIG. 8 is an example of a flowchart of time slot return request processing. In this process, the communication device B requests the communication device A to return the distributed time slot.

First, the communication device B transmits a time slot return request message to the communication device A (801). The time slot return request message describes the number of time slots requesting return, the number of time slots requesting return, the urgency of return, and the like.

Communication apparatus A checks whether there is a time slot that can be returned (802). When there is a time slot that can be returned to the communication device A (802: Yes), the time slot is returned to the communication device B, and the transmission timing management table 119 and the self information management table 119 are updated (803). On the other hand, if there is no time slot that can be returned to the communication device A (802: No), a non-returnable message indicating that the time slot cannot be returned is transmitted to the communication device B (804).

When the communication apparatus B receives the non-returnable message, the communication apparatus B determines whether or not to force the return of all time slots (805). If the communication device B determines that a forced return should be requested (805: Yes), it transmits a slot forced return request message to the communication device A (806), and proceeds to step 809. On the other hand, when the communication apparatus B determines that it is not necessary to request forcible return (805: No), the process proceeds to step 809. When there is a forced return request, the time slot must be returned to the communication device B even if the communication device A loses all the time slots due to the return of the time slot. For example, the communication device B acquires all the time slots from the communication device A whose rank is lower than that of the own device and distributes the time slots to other communication devices whose rank is higher than that of the own device. It is necessary to do this.

The communication device A receives the time slot forced return request message from the communication device B, executes a time slot return process (807), and transmits a time slot return message to the communication device B (808).

The communication device B confirms the time slot returned from the communication device A, and updates the transmission timing management table 119 and the self information management table 119 (809).

Further, the communication device A changes the route when all of the time slots held by the communication device A are lost and it is necessary to acquire time slots from another communication device (810).

In the flowchart of FIG. 8, the communication device A returns the time slot in response to the time slot return request from the communication device B, but instead of this, the communication device A autonomously communicates with the communication device B. You may return the time slot. For example, the communication device A newly acquires a time slot from another more effective communication device, and the time slot acquired from the communication device B becomes unnecessary.

FIG. 9 is an example of a flowchart of time slot arbitration processing. In this process, the communication device A receives a time slot request from the communication device C, but the communication device A does not hold a time slot that can be distributed to the communication device C.

First, the communication device C transmits a time slot request message to the communication device A (901).

The communication device A that has received the time slot request message executes time slot arbitration because there is no time slot that can be distributed (902). This process is the same as the process described with reference to FIG.

The communication device A determines a time slot arbitration method (903). The arbitration method is determined by, for example, selecting a communication device that should request a time slot and a time that should be requested in consideration of the distribution priority of the communication device C that is the time slot request source and the rank of other communication devices. Determine the number of slots. For example, the local apparatus normally requests the communication apparatus that has allocated the time slot to return the time slot. However, if the priority of the communication device that requested the time slot is high and the time slot is not returned from the communication device distributed by the device itself, the communication device that has been distributed to the device itself Further, a request for a time slot may be defined.

Here, it is assumed that the communication device A requests a time slot from the communication device B, and further the communication device B requests a time slot from the communication device D ahead.

As a continuation of step 903, the communication device A transmits a time slot request message to the communication device B (904).

The communication device B that has received the time slot request message transmits a standby message to the communication device A so as to wait for an answer because there is no time slot that can be distributed (905).

The communication device B transmits a time slot request message to the communication device D (909).

The communication device A receives the standby message transmitted from the communication device B in step 905, and sets a timeout time (906). After the timeout period ends (907: Yes), the communication device A retransmits the time slot request message to the communication device B as necessary (908).

On the other hand, when the communication device D receives the time slot request message in step 909, it returns a time slot request response message to the communication device B, and distributes the time slot.

Communication apparatus B confirms the received time slot request response message (910). The communication apparatus B returns a time slot request response message to the communication apparatus A, and distributes the time slot allocated from the communication apparatus D to the communication apparatus A.

Communication apparatus A confirms the received time slot request response message (911). The communication apparatus A transmits a time slot request response message to the communication apparatus C, and distributes the time slot allocated from the communication apparatus B to the communication apparatus C.

The communication device C receives the time slot request response message and acquires the time slot.

Note that the type of communication device requesting a time slot and the range requesting the time slot may be specified. Further, the number of time slots to be distributed may be increased or decreased according to the state and communication quality of the communication path to which the own apparatus is connected or the priority of the communication apparatus that has requested the time slot. For example, applications that need to communicate urgently allow time slot arbitration with a wide range of communication devices so that time slots can be acquired preferentially, and applications that do not require regular communication are time slots. The arbitration range may be limited.

According to the present embodiment, when a plurality of (many) communication devices transmit data to a specific communication device (data collection device) in an ad hoc network, the transmission timing is adjusted autonomously between the communication devices. be able to. Therefore, in this embodiment, there is no need to provide a management server for centrally controlling the transmission timing of each communication device. For this reason, in this embodiment, it is possible to prevent a large amount of data for adjusting the transmission timing from flowing through the network, to secure a band used for sensing data communication, and to collect sensing data with high reliability. Can do.

Example 2 will be described with reference to FIG. Each of the following embodiments including this embodiment corresponds to a modification of the first embodiment. Therefore, the difference from the first embodiment will be mainly described. FIG. 11 is an explanatory diagram showing an example of a time slot distribution method in consideration of changes in the network topology.

FIG. 11 (a) is an explanatory diagram when only a necessary number of time slots are distributed at any time.

As shown on the left side of FIG. 11A, the communication device 1101a (A) distributes one time slot to the communication device 1102a (B). Thereafter, it is assumed that the communication apparatuses 1103a (C) and 1104a (D) are connected to the communication apparatus 1102a (B). At this time, the communication device 1102a (B) cannot distribute its own time slot 1112a.

Therefore, as shown on the right side of FIG. 11A, the communication device 1102a (B) performs time slot arbitration with the communication device 1101a (A), and acquires two

time slots

1121a and 1122a from the communication device 1101a (A). To do. The communication device 1102a (B) distributes the two time slots acquired previously to the communication devices 1103a (C) and 1104a (D), respectively.

FIG. 11B is an explanatory diagram when a large number of time slots are distributed in advance with a margin.

As shown on the left side of FIG. 11 (b), the communication device 1101b (A) distributes three time slots 1102b to the communication device 1102b (B). Thereafter, it is assumed that the communication devices 1103b (C) and 1104b (D) are connected to the communication device 1102b (B).

As shown on the right side of FIG. 11 (b), since the communication device 1102b (B) holds an extra time slot, its two

time slots

1121b and 1122b are assigned to the communication devices 1103b (C) and 1104b (D). ).

Hereinafter, the communication devices 1101a (A) and 1101b (A) are communication devices (A), the communication devices 1102a (B) and 1102b (B) are communication devices (B), and the communication devices 1103a (C) and 1103b (C). ) May be referred to as a communication device (C), and the communication devices 1104a (D) and 1104b (D) may be referred to as a communication device (D).

The merit of the configuration shown in FIG. 11A is that a finite number of time slots can be used efficiently without waste. Since the required number of time slots are distributed to the necessary communication devices as needed, the number of time slots that are not used despite being distributed is reduced and can be used efficiently.

On the other hand, the demerit of the configuration shown in FIG. 11A is that there is a new time slot request from the other communication devices (C) and (D) to the communication device (B) that has allocated time slots. When it comes to time slot arbitration. Each time slot arbitration is executed, a slot request or the like is executed in the distribution source communication device (B), so that the network is congested and the usable communication band is narrowed.

The merit of the configuration shown in FIG. 11B is that the number of timeslot arbitration processing can be reduced. When there is a time slot request from another communication device (C) or (D) to the communication device (B) that has received the time slot allocation, the communication device (B) that has received the time slot allocation. ) Holds an extra time slot, so that the time slot can be immediately distributed to other communication apparatuses (C) and (D) without performing the time slot arbitration process.

On the other hand, the disadvantage of FIG. 11B is that there is a high possibility that the number of time slots that are not used in spite of the distribution will increase. For this reason, there is a possibility that the communication band cannot be used efficiently.

Which is appropriate depends on the target system and application. For example, when the communication devices are powered off simultaneously due to a power failure and then electricity is restored, all the communication devices execute a time slot request. In this case, according to the method of FIG. 11 (b), a communication device with a higher rank, such as a data collection device, allocates a time slot with a margin in advance to a communication device with a lower rank. In addition, frequent occurrence of time slot arbitration can be prevented.

Similarly, for example, when a communication device serving as a gateway for each residence is provided under the data collection device serving as a gateway for the entire apartment house, a large number of time slots are allocated to the communication devices for each residence. Good. A plurality of other communication devices may be connected under the communication device serving as a gateway for each residence, and these other communication devices may start transmitting sensing data all at once. It is.

Example 3 will be described with reference to FIG. FIG. 12 is an explanatory diagram showing an example of a time slot distribution method considering communication characteristics.

In FIG. 12, the communication devices 1202 (B) and 1203 (C) are connected by a communication path having a relatively low communication speed, such as a specific low power radio. It is assumed that the communication devices 1202 (B) and 1203 (D) are connected by a communication path having a relatively high communication speed such as a wireless LAN.

One time slot is set to be short in accordance with a high-speed communication path. Many (eg, five) time slots 1213 are allocated to the communication device 1203 (C) connected to the low-speed communication path. A small number of (for example, one) time slots 1214 are allocated to the communication device 1204 (D) connected to the high-speed communication path.

Although the communication speed between the communication devices 1202 (B) and 1203 (C) is slow, a long communication time can be secured, so that a predetermined amount of data can be transmitted from the communication device 1203 (C) to the communication device 1202 (B). . On the other hand, since the communication speed between the communication devices 1202 (B) and 1203 (D) is high, a predetermined amount of data can be transmitted even if the communication time is short.

In other words, when the communication speed of each communication device is different, the size of the time slot is set according to the fastest communication speed, and the time slot to be distributed to each communication device is set according to the communication speed of each communication path. Change the number. Thereby, the time slot can be efficiently used as the entire system.

Note that, for example, the communication device 1203 (C) having a low communication speed, such as a specific low-power radio, may have a configuration in which time slots are not distributed to other communication devices in principle. This is because a communication apparatus having a low communication speed can secure data in a necessary number of time slots and transfer data.

In addition, when the communication quality of each communication device is different, the number of time slots to be distributed may be changed according to the communication quality. For example, consider a case where the rank of a communication device changes depending on the communication quality of wireless communication. In that case, the number of necessary time slots also changes depending on the rank of the communication device. The lower the communication quality, the more timeslots are needed.

When dynamically adjusting the number of time slots to be allocated according to the communication quality, if the communication quality of wireless communication changes frequently, the rank of the communication device is changed frequently. As a result, the number of time slots required by the communication apparatus also changes frequently, so that the communication apparatus repeats the return and acquisition of the time slots. If the return and acquisition of time slots are frequently repeated, the ad hoc network becomes congested and the band for transmitting sensing data becomes narrow.

Therefore, it is desirable to allocate time slots with a sufficient margin in advance so that return of time slots and acquisition of time slots are not repeated frequently even if the rank of the communication device changes.

In addition, when the communication quality of wireless communication is unstable, a configuration in which no time slot is allocated to the communication device may be used. A communication device that has not been assigned a time slot cannot transmit sensing data to the data collection device. However, stable communication is possible over the entire sensor network. Even if some communication devices are disconnected from the sensor network, processing such as remote monitoring or remote control may be performed using sensing data from other communication devices. A communication apparatus that can be replaced by another communication apparatus can be configured so as not to assign time slots only during a period when the communication quality is unstable.

In this embodiment, an example of how to use time slots will be described. The role of the time slot is used to link the time slot and the transmission timing of the sensing data so that the sensing data reaches the data collection device.

Therefore, for normal data, for example, only data that needs to be transmitted autonomously by CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) to prevent collisions, as described in each of the above-described embodiments. You may transmit using a slot.

Normal sensing data (and routing control messages, etc.) are transmitted using CSMA / CA. The urgent data is transmitted using the time slot according to the present invention. The urgent data is, for example, control data that needs to reach the data collection device at a predetermined time, or data that cannot be lost during communication. In other words, since data used in so-called mission critical processing needs to be collected within a predetermined time, highly reliable communication is required. In such a case, the time slot according to the present invention is used to deliver data with high reliability.

This makes it possible to build a system that achieves both best-effort communication and reliable communication using time slots.

Example 5 will be described with reference to FIG. In the first embodiment, a case has been described in which time slot numbers are assigned consecutively. In the fifth embodiment, a case will be described in which time slots are exchanged between communication devices regardless of continuity of numbers.

FIG. 13 is an explanatory diagram showing a time slot distribution method according to this embodiment.

Suppose that each communication device is assigned a time slot that is not a sequential number, as shown in FIG. For example, the communication device (B) located under the original communication device (A) holds the fourth time slot. The communication device (C) located under the communication device (A) together with the communication device (B) has a seventh time slot. One communication device (D) located under the communication device (B) has the first and third time slots. The other communication device (E) located under the communication device (B) has second and fifth time slots. One communication device (F) located below the communication device (C) has

time slots

6 and 8, and the other communication device (G) located below the communication device (C) is 9 Number and 10 time slots.

Describes the data transmission method using time slots. First, the communication device (D) transmits data to the communication device (B) at the timing of the first time slot 1311. Next, the communication device (E) transmits data to the communication device (B) at the timing of the second time slot 1312.

The communication device (D) transmits data to the communication device (B) at the timing of the third time slot. The communication device (B) transmits its own data and data received from the communication devices (D) and (E) to the communication device (A) at the timing of the fourth time slot 1304.

Thereby, the data collected by the communication devices (D) and (E) by the sensor or the like can be transmitted to the communication device (A) which is the data collection device.

In this embodiment, the communication device that relays data needs to temporarily hold the data to be relayed until the order in which the time slot held by the communication device is executed comes. For example, in the above example, the communication device (B) needs to temporarily hold data received from the communication devices (D) and (E).

The merit of the configuration in which the time slot numbers are assigned is that the processing load on each communication device can be reduced. Each communication device does not need to calculate how the time slots can be allocated by serial numbers when distributing the time slots.

One disadvantage is that a communication device that relays data needs to increase the size of the buffer memory in order to temporarily hold the data. Another disadvantage is that the time for the data to reach the data collection device is somewhat delayed.

∙ Which method is appropriate, the method of managing the time slot numbers continuously or the method of managing the numbers regardless of the order of the numbers, depends on the capability of the system and communication device to be applied. Therefore, either one of the methods may be set in advance, or the two methods may be automatically switched according to the status of the communication device.

The embodiment described above is an example for explaining the present invention, and is not intended to limit the scope of the present invention to the embodiment. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

DESCRIPTION OF

SYMBOLS

100, 101 ... Communication apparatus 113 ... Communication part 114 ... Memory | storage part 115 ... Communication control part 116 ... Ad hoc network communication control part 117 ... Transmission timing management control part 118 ... Ad hoc network communication route table 119 ... Transmission timing management table 120 ... Self-information Management tables 130, 131 ...

network

140, 141 ... server

Claims

A communication device belonging to an ad hoc network in which a plurality of communication devices are connected to each other by wireless communication,
A communication unit that transmits and receives data;
A time slot management unit for managing a time slot, the time slot management unit managing the time slot indicating information on timing of transmitting the data to another communication device belonging to the ad hoc network;
A transmission timing management control unit that acquires the time slot from the other communication device through the communication unit or distributes the time slot to the other communication device. A transmission timing management control unit for managing the time slot management unit and transmitting the data to the other communication device through the communication unit based on the timing described in the time slot managed by the time slot management unit;
An ad hoc network communication device.
The transmission timing management control unit determines the number of time slots to be acquired from the other communication device or distributed to the other communication device based on a predetermined condition.
The ad hoc network communication apparatus according to claim 1.
The ad hoc network is a tree-type network;
The ad hoc network is provided with a predetermined communication device for collecting the data,
The transmission timing management control unit acquires or distributes to the other communication device from the other communication device based on a logical network distance to the predetermined communication device as the predetermined condition. Determine the number of timeslots;
The ad hoc network communication apparatus according to claim 2.
The transmission timing management control unit is acquired from the other communication device based on a communication bandwidth with the other communication device that acquires or distributes the time slot as the predetermined condition, or Determining the number of time slots to be distributed to other communication devices;
The ad hoc network communication apparatus according to claim 2.
The transmission timing management control unit distributes more time slots to the other communication device when the communication band is narrow than when the communication band is wide.
The ad hoc network communication apparatus according to claim 4.
The communication device holds a rank value representing the priority of the device,
The transmission timing management control unit, as the predetermined condition, based on a difference between a rank value held by the own device and a rank value held by the other communication device that acquires or distributes the time slot, Determining the number of timeslots obtained from or distributed to other communication devices;
The ad hoc network communication apparatus according to claim 2.
The transmission timing management control unit manages the time slots by serial numbers, and can distribute a plurality of continuous time slots to the other communication devices or obtain from the other communication devices.
The ad hoc network communication apparatus according to claim 1.
The transmission timing management control unit confirms whether or not it is connected to the other communication device, and if the connection with the other communication device cannot be confirmed, the time slot allocated to the other communication device Recover,
The ad hoc network communication apparatus according to claim 1.
The transmission timing management control unit requests acquisition of a time slot from a third communication device belonging to the ad hoc network when a time slot to be distributed to the other communication device is insufficient.
The ad hoc network communication apparatus according to claim 1.
A communication device belonging to an ad hoc network in which a plurality of communication devices are connected to each other by wireless communication,
Each of the communication devices is
A time slot indicating information related to timing for transmitting predetermined data to another communication device is acquired from the other communication device or distributed to the other communication device;
Based on the timing described in the time slot held by the own device, the data held by the own device is transmitted to the other communication device.
Ad hoc network communication method.
An ad hoc network system in which a plurality of communication devices are connected to each other by wireless communication,
The plurality of communication devices include:
A communication unit that transmits and receives data;
A time slot management unit for managing a time slot, the time slot management unit managing the time slot indicating information on timing of transmitting the data to another communication device belonging to the ad hoc network;
A transmission timing management control unit that acquires the time slot from the other communication device through the communication unit or distributes the time slot to the other communication device. A transmission timing management control unit for managing the time slot management unit and transmitting the data to the other communication device through the communication unit based on the timing described in the time slot managed by the time slot management unit;
Ad hoc network system.